DESCRIPTION

Mustache can be used for HTML, config files, source code - anything. It
works by expanding tags in a template using values provided in a hash
or object.
We call it "logic-less" because there are no if statements, else
clauses, or for loops. Instead there are only tags. Some tags are
replaced with a value, some nothing, and others a series of values.
This document explains the different types of Mustache tags.

TAGTYPES

Tags are indicated by the double mustaches. {{person}} is a tag, as is
{{#person}}. In both examples, we'd refer to person as the key or tag
key. Let's talk about the different types of tags.
Variables
The most basic tag type is the variable. A {{name}} tag in a basic
template will try to find the name key in the current context. If there
is no name key, nothing will be rendered.
All variables are HTML escaped by default. If you want to return
unescaped HTML, use the triple mustache: {{{name}}}.
You can also use & to unescape a variable: {{&name}}. This may be
useful when changing delimiters (see "Set Delimiter" below).
By default a variable "miss" returns an empty string. This can usually
be configured in your Mustache library. The Ruby version of Mustache
supports raising an exception in this situation, for instance.
Template:
* {{name}}
* {{age}}
* {{company}}
* {{{company}}}
Hash:
{
"name": "Chris",
"company": "<b>GitHub</b>"
}
Output:
* Chris
*
* &lt;b&gt;GitHub&lt;/b&gt;
* <b>GitHub</b>
Sections
Sections render blocks of text one or more times, depending on the
value of the key in the current context.
A section begins with a pound and ends with a slash. That is,
{{#person}} begins a "person" section while {{/person}} ends it.
The behavior of the section is determined by the value of the key.
FalseValuesorEmptyLists
If the person key exists and has a value of false or an empty list, the
HTML between the pound and slash will not be displayed.
Template:
Shown.
{{#nothin}}
Never shown!
{{/nothin}}
Hash:
{
"person": true,
}
Output:
Shown.
Non-EmptyLists
If the person key exists and has a non-false value, the HTML between
the pound and slash will be rendered and displayed one or more times.
When the value is a non-empty list, the text in the block will be
displayed once for each item in the list. The context of the block will
be set to the current item for each iteration. In this way we can loop
over collections.
Template:
{{#repo}}
<b>{{name}}</b>
{{/repo}}
Hash:
{
"repo": [
{ "name": "resque" },
{ "name": "hub" },
{ "name": "rip" },
]
}
Output:
<b>resque</b>
<b>hub</b>
<b>rip</b>
Lambdas
When the value is a callable object, such as a function or lambda, the
object will be invoked and passed the block of text. The text passed is
the literal block, unrendered. {{tags}} will not have been expanded -
the lambda should do that on its own. In this way you can implement
filters or caching.
Template:
{{#wrapped}}
{{name}} is awesome.
{{/wrapped}}
Hash:
{
"name": "Willy",
"wrapped": function() {
return function(text) {
return "<b>" + render(text) + "</b>"
}
}
}
Output:
<b>Willy is awesome.</b>
Non-FalseValues
When the value is non-false but not a list, it will be used as the
context for a single rendering of the block.
Template:
{{#person?}}
Hi {{name}}!
{{/person?}}
Hash:
{
"person?": { "name": "Jon" }
}
Output:
Hi Jon!
InvertedSections
An inverted section begins with a caret (hat) and ends with a slash.
That is {{^person}} begins a "person" inverted section while
{{/person}} ends it.
While sections can be used to render text one or more times based on
the value of the key, inverted sections may render text once based on
the inverse value of the key. That is, they will be rendered if the key
doesn't exist, is false, or is an empty list.
Template:
{{#repo}}
<b>{{name}}</b>
{{/repo}}
{{^repo}}
No repos :(
{{/repo}}
Hash:
{
"repo": []
}
Output:
No repos :(
Comments
Comments begin with a bang and are ignored. The following template:
<h1>Today{{! ignore me }}.</h1>
Will render as follows:
<h1>Today.</h1>
Comments may contain newlines.
Partials
Partials begin with a greater than sign, like {{>box}}.
Partials are rendered at runtime (as opposed to compile time), so
recursive partials are possible. Just avoid infinite loops.
They also inherit the calling context. Whereas in ERB you may have
this:
<%= partial :next_more, :start => start, :size => size %>
Mustache requires only this:
{{> next_more}}
Why? Because the next_more.mustache file will inherit the size and
start methods from the calling context.
In this way you may want to think of partials as includes, or template
expansion, even though it's not literally true.
For example, this template and partial:
base.mustache:
<h2>Names</h2>
{{#names}}
{{> user}}
{{/names}}
user.mustache:
<strong>{{name}}</strong>
Can be thought of as a single, expanded template:
<h2>Names</h2>
{{#names}}
<strong>{{name}}</strong>
{{/names}}
SetDelimiter
Set Delimiter tags start with an equal sign and change the tag
delimiters from {{ and }} to custom strings.
Consider the following contrived example:
* {{default_tags}}
{{=<% %>=}}
* <% erb_style_tags %>
<%={{ }}=%>
* {{ default_tags_again }}
Here we have a list with three items. The first item uses the default
tag style, the second uses erb style as defined by the Set Delimiter
tag, and the third returns to the default style after yet another Set
Delimiter declaration.
According to ctemplates, this "is useful for languages like TeX, where
double-braces may occur in the text and are awkward to use for markup."
Custom delimiters may not contain whitespace or the equals sign.